To clarify the issue about \(\xi _{\Delta i}\)  and \(\xi _{\Psi i}\) , we consider the two-band generalization of the BCS model [1]}, [2]} with the \(s\) -wave pair condensates in both bands governed by the symmetric coupling matrix \(g_{ij}\,(i,j=1,2)\) . To solve the microscopic formalism, we employ the Bogoliubov-de Gennes (BdG) equations, which for the case of interest are written in the form [3]}
\(\left[\begin{array}{cc}\hat{H}_{ei} & \Delta _i({\bf r}) \\\Delta _i^*({\bf r}) & -\hat{H}^*_{ei}\end{array}\right] \left[\begin{array}{c}u_{i\nu }({\bf r}) \\v_{i\nu }({\bf r})\end{array}\right] = E_{i\nu }\left[\begin{array}{c}u_{i\nu }({\bf r}) \\v_{i\nu }({\bf r})\end{array}\right],\) 
